Hose pump

ABSTRACT

A hose pump includes a hose bed having a counter support, a carrier disk rotatable relative to the counter support, and a number of pinch rollers and guide rollers arranged on the carrier disk. A guide roller is arranged between two consecutive pinch rollers, and the pinch rollers press a hose inserted into hose bed against the counter support, while pinching the hose when the carrier disk is rotating in the conveying direction to transport the fluid in the hose. To ensure reliable threading of a hose section of a pump hose, when the hose section is somewhat too short and to prevent unthreading of the inserted hose section during operation of the hose pump, the angular distance between a guide roller and the pinch roller preceding the guide roller in the conveying direction is greater than the angular distance between this guide roller and the pinch roller following the guide roller in the conveying direction.

FIELD OF THE DISCLOSURE

The disclosure relates to a hose pump.

BACKGROUND

Such hose pumps are known, for example, from DE 10 2014 104 320 B1 and DE 102010 000 594 A1. These known hose pumps have a hose bed into which a hose section of a hose bent into a loop can be inserted. The known hose pumps also include a counter support and a carrier disk rotatable relative to the counter support, on whose top a number of pinch rollers and a number of guide rollers are arranged. Both the pinch rollers and the guide rollers are arranged equidistant from each other in the radially outer area of the carrier disk and in the peripheral direction of the carrier disk, one guide roller each being arranged between two consecutive pinch rollers in the peripheral direction of the carrier disk. For example, three pinch rollers and three guide rollers are provided in an embodiment example of the known hose pumps, which have an angular distance of 60° relative to the adjacent pinch roller or guide roller in the peripheral direction of the carrier disk. The pinch rollers have a smooth outer periphery and press a hose inserted into the hose bed against the counter support, while squeezing the hose, when the carrier disk is rotating in a conveying direction, in order to transport fluid situated in the hose in the conveying direction. The cylindrical guide rollers have a guide groove running in the peripheral direction on their outer periphery to accommodate the radially inner hose half of the hose section and ensure exact positioning and guidance of the hose in the hose bed both during threading of the hose section into the hose bed and during pump operation.

A motor-driven threading device, as described, for example, in EP 2542781, can be used for automated threading of the hose section into the hose bed. As an alternative, the hose section can also be pressed with a hold-down device against a support surface at the entry to the hose bed during threading into the hose bed and can be grasped by one of the guide rollers, while the carrier disk is being rotated, and then pulled into the hose bed, in which case the radially inner area of the hose section is taken up in the guide groove of the guide roller and press downward in the axial direction onto a support surface in the hose bed. Problems can occur in this case when the hose section is too short. There is then the risk that the unduly short hose section will be stretched while being threaded and placed under tensile stress, and thereby slip out of the guide groove of the guide roller.

When the hose section inserted into the hose bed is too long, problems can occur during operation of the known hose pumps because the hose section at the output of the hose bed forms a loop protruding above the support surface of the hose bed and is therefore not cleanly guided in the hose bed. In particular, at very high pump pressures, which can reach up to 20 bar during the intended operation of the hose pump, there is the risk that the downstream end of the hose section inserted into the hose bed will slip out of the guide groove of the guide rollers and thereby be raised from the support surface of the hose bed. This can mean that the hose section automatically and undesirably unthreads during operation of the hose pump.

SUMMARY OF THE DISCLOSURE

Starting from the foregoing, one embodiment of the disclosure modifies a generic hose pump so that reliable threading of the hose section of a pump hose can also be ensured when the hose section is somewhat too short in comparison with the inner periphery of the counter support. Automatic unthreading of the inserted hose section is also to be prevented during operation of the hose pump, especially under high pump pressures, and the service life of the pump hose can be lengthened.

Other preferred embodiments of the hose pump are also disclosed.

In an embodiment, the hose pump according to the disclosure has a hose bed for insertion of a hose section of a pump hose, a counter support, a carrier disk rotatable relative to the counter support, a number of pinch rollers arranged on the carrier disk equidistant from each other in the peripheral direction and a number of guide rollers arranged on the carrier disk equidistant from each other in the peripheral direction, one guide roller being arranged between two consecutive pinch rollers in the peripheral direction of the guide disk, and the pinch rollers press a hose (hose section) inserted into the hose bed against the counter support, while squeezing the hose as the carrier disk is rotating in the conveying direction, in order to transport a fluid situated in the hose in the conveying direction.

Unlike the known hose pumps cited above, the pinch rollers and guide rollers in the hose pump according to the disclosure are not all arranged symmetrically over the periphery of the carrier disk equidistant from each other. The guide rollers in the hose pump according to the disclosure are set back with reference to the pinch rollers following them in the conveying direction (direction of rotation of the carrier disk during pump operation of the hose pump), i.e., the angular distance (δ) between a guide roller and the pinch roller following this guide roller in the conveying direction is smaller than the angular distance (Δ) between this guide roller and the pinch roller preceding this guide roller in the conveying direction.

This arrangement of the pinch rollers and the guide rollers on the carrier disk prevents the upstream section of the hose from slipping out of the guide groove of the guide roller during threading of the hose into the hose bed, because, during rotation of the carrier disk, the guide roller directly (i.e., with only a small angular distance δ) follows a pinch roller, which presses the upstream section of the hose against the counter support and thereby fixes the position in the hose bed of the section of the hose already introduced to the hose bed.

Due to of the arrangement of the pinch rollers and the guide rollers on the carrier disk according to the disclosure, during pump operation of the hose pump, undesired unthreading of the hose is prevented, because each pinch roller during rotation of the carrier disk directly, i.e., at only a small angular distance δ, leads a guide roller, which reliably secures the downstream section of the hose even at high pump pressures in the hose bed and prevents the downstream end of the hose at the output of the hose bed from bulging into a loop while the section of the hose lying somewhat farther back in the conveying direction is pressed against the counter support by the pinch roller.

The magnitude of the relative angular difference (Δ−δ/Δ+δ) between the angular distance Δ between the guide roller and the pinch roller preceding this guide roller in the conveying direction and the angular distance δ between this guide roller and the pinch roller following this guide roller in the conveying direction is preferably in the range from 0.2 to 0.5.

The guide rollers and the pinch rollers are expediently arranged rotationally symmetrically on the carrier disk (with reference to the axis of rotation of the carrier disk as center of symmetry), the angle of symmetry being 360°/n, where n is the number of guide rollers and pinch rollers.

In a preferred embodiment, the hose pump according to the disclosure has three or more pinch rollers and an equal number of guide rollers, which are arranged on the radial outer edge of the carrier disk, so that the angular distance (δ) between each guide roller and the pinch roller following the guide roller in the conveying direction is less than 60°, and, in the case of three guide rollers and three pinch rollers, preferably 45°. Correspondingly, the angular distance (Δ) between a guide roller and the pinch roller preceding this guide roller in the conveying direction is greater than 60° and particularly at least 75°. In this arrangement with three pinch rollers and three guide rollers the magnitude of the relative angular distance preferably lies at Δ−δ/Δ+δ=0.25. In an alternative arrangement with four pinch rollers and four guide rollers, the magnitude of the relative angular distance preferably lies at Δ−δ/Δ+δ=0.33.

According to an aspect of the disclosure independent of the arrangement of pinch rollers and guide rollers on the carrier disk or combinable with it, a cylinder protruding above the surface of the carrier disk is arranged in the center of the carrier disk coaxial to its axis of rotation, the outside diameter of which at least roughly reaches the outer periphery of the pinch rollers and guide rollers lying radially farther outward. The cylinder, located radially inward relative to the guide rollers and the pinch rollers on the carrier disk, prevents a section of the hose from lying on a radially inner (relative to the carrier disk) portion of the outer periphery of the guide rollers during threading of the hose and therefore from not being correctly grasped by this guide roller, and it can be introduced into the hose bed between the outer periphery of the guide roller and the counter support. It is expedient for this purpose if the radial distance between the outer surface of the cylinder and the outer periphery of the guide rollers is smaller than the diameter of the hose being introduced to the hose bed.

In order to rotate the carrier disk during operation of the pump, the carrier disk is connected to a shaft which is coupled to a drive and can be placed in rotation by it. The guide rollers and the pinch rollers are preferably mounted to rotate on the carrier disk in order to permit frictionless rolling on the surface of the hose. However, they can also be non-rotatably connected to the carrier disk. The axis of rotation of the carrier disk (axis of the shaft) and the axes of the pinch rollers and guide rollers then run parallel to each other. If the guide rollers and the pinch rollers are mounted to rotate on the carrier disk, they can be placed in rotation by a drive (optionally via a gear mechanism), in which the drive is preferably a drive that also rotates the carrier disk. The guide rollers and the pinch rollers, however, can also be mounted to rotate on the carrier disk without coupling to a drive.

The pinch rollers are expediently made at least essentially cylindrical and with a smooth outer surface, the outer periphery of the pinch rollers that presses the hose against the counter support being formed by the smooth outer surface. The guide rollers expediently have on their outer periphery a continuous guide groove, which is adapted to the shape of the hose and is designed with a semicircular cross section, for example, for a hose with a circular cross section. Owing to shaping of the guide groove on the outer periphery of the guide rollers, these guide rollers are nestled on the surface of the hose without squeezing it, when the hose pump is running. Reliable and uniform guidance of the hose in the hose bed is thus ensured when the hose pump is running.

BRIEF DESCRIPTION OF THE DRAWINGS

These and additional advantages and features of the hose pump according to the disclosure are apparent from the embodiment example described below with reference to the accompanying drawings. The drawings show:

FIG. 1: Perspective view of a hose pump according to the disclosure with hose inserted therein;

FIG. 2: Cross section of the hose pump of FIG. 1 (without hose).

DETAILED DESCRIPTION

An embodiment example of a hose pump according to the disclosure is shown in FIG. 1 and FIG. 2 in a perspective view (with inserted hose 16) and a sectional view (without hose). The hose pump serves to convey a fluid guided in a hose 16 or an injection fluid for a medical, especially intravenous, injection. The hose pump is arranged in a pump housing 14, on which a pivotable housing cover is connected by means of a fastening device 18, not shown here for reasons of improved clarity.

The hose pump comprises a carrier disk 1, which is coupled via a drive shaft 10 arranged centrally in the carrier disk 1 to a drive 7. The drive 7 is an electric motor, for example. When drive 7 is running, the carrier disk 1 is placed in rotation about an axis of rotation A in conveying direction F, via the drive shaft 10, which is non-rotatably connected to carrier disk 1. The conveying direction F in the depicted embodiment example (direction of rotation of the carrier disk during pump operation) is clockwise.

The hose pump also comprises a hose bed 2 with a hose input 2a and a hose output 2b, as well as a counter support 4. The counter support 4 is formed by the inner periphery of a circular segment, which is open in the area of the hose input 2 a and the hose output 2 b of hose bed 2 to introduce a hose 16. The hose bed 2 serves to accommodate a hose section of a pump hose (the hose section is hereinafter referred to as a hose), in which a fluid (for example, an injection fluid for intravenous injection into the bloodstream of a patient) is guided. A hose inserted into hose bed 2 then lies on a guide surface 2 c formed by the surface of carrier disk 1. The counter support 4 runs tangentially outwards in the area of hose output 2 b of hose bed 2, as is apparent from the figures.

Several pinch rollers 3 are arranged on the surface of the carrier disk 1 in the radially outer section (near its outer periphery). The axes 3′ of the pinch rollers then lie on a circular path concentric to the axis of rotation (A) of carrier disk 1 (dashed line in FIG. 2). In the embodiment example of the hose pump according to the disclosure illustrated here, three such pinch rollers 3 a, 3 b, 3 c are provided and are distributed uniformly over the periphery of carrier disk 1. If reference is subsequently made to identically designed pinch rollers 3 a, 3 b, 3 c, reference numeral 3 is used. The pinch rollers 3 are at least essentially cylindrical with a smooth outer surface.

A guide roller 5 is arranged on carrier disk 1 between adjacent pinch rollers 3. The axes 5′ of the guide rollers 5 then also lie on the circular path (dashed line in FIG. 2) running concentric to axis or rotation (A) of carrier disk 1. In the embodiment example of the hose pump according to the disclosure illustrated here, three such guide rollers 5 a, 5 b, 5 c are provided and are arranged uniformly distributed over the periphery of carrier disk 1 (and on the dashed circular path). If reference is subsequently made to identically formed guide rollers 5 a, 5 b, 5 c, reference numeral 5 is used.

The guide rollers 5 have a cylindrical basic shape and a continuous guide groove 11 in the peripheral direction on their outer periphery (on the cylinder surface). Both the pinch rollers 3 and the guide rollers 5 are expediently mounted to rotate on carrier disk 1, the axes of rotation 3′ of the pinch rollers 3 and the axes of rotation 5′ of the guide rollers 5 each running parallel to drive shaft 10. The pinch rollers 3 and the guide rollers 5 can then be mounted either to rotate freely on carrier disk 1 or also coupled to drive 7 via a clutch. If the pinch rollers 3 and/or the guide rollers 5 are coupled via a clutch to drive 7, they are placed in rotation in the same direction as carrier disk 1 (clockwise) when drive 7 is running.

The three pinch rollers 3 a, 3 b, 3 c and the three guide rollers 5 a, 5 b, 5 c are arranged on the radial outer edge of carrier disk 1 so that the angular distance δ between each guide roller and the pinch roller following a guide roller in the conveying direction is less than 60° and, as in the depicted embodiment example of FIGS. 1 and 2, especially 45° . Correspondingly, the angular distance Δ between a guide roller and the pinch roller preceding this guide roller in the conveying direction is greater than 60° and amounts to 75° in the depicted embodiment example. In the embodiment example depicted in FIGS. 1 and 2, the angular distance δ between the guide roller 5 a and the pinch roller 3 a following this guide roller 5 a in conveying direction F, δ=45°. Correspondingly, the angular distance A between the guide roller 5 a and the pinch roller 3 b preceding this guide roller 5 a in the conveying direction lies at Δ=75°.

A hose inserted into hose bed 2 is guided by the guide rollers 5 by engaging the hose in the peripheral guide grooves 11 of the guide rollers. The hose is thus held on the guide surface 2 c formed by the surface of carrier disk 1 and the slipping out of the hose from the hose bed 2 is prevented when the pump is running.

In the center of carrier disk 1, a cylinder 6 protruding above the surface of carrier disk 1 coaxial to its axial of rotation A is arranged, which encloses drive shaft 10 and whose (outside) diameter D at least roughly reaches the outer periphery of the pinch rollers and guide rollers lying radially farther outward, i.e., a small (as possible) distance exists between the outer periphery of cylinder 6 and the outer periphery of the pinch rollers and guide rollers (FIG. 1). The cylinder 6, as is apparent from FIG. 2, can be designed as a hollow cylinder or also as a solid cylinder. The cylinder 6 is expediently non-rotatably connected to carrier disk 1. During threading of the hose, the cylinder 6 prevents the hose from lying on the radially inwardly pointing side of the guide rollers 5 and therefore from not being properly threaded into the hose bed 2 between the outer periphery of the pinch rollers 3 and the counter support 4. For this purpose, the radial distance between the outer surface of the cylinder and the outer periphery of the guide rollers should be less than the diameter of the hose being introduced into the hose bed. The height of the cylinder 6 (in the axial direction) is then expediently adjusted to the height of the pinch rollers and the guide rollers and has at least the same height as the pinch rollers and the guide rollers. The cylinder 6 expediently protrudes somewhat beyond the pinch rollers and the guide rollers in the axial direction in order to permit unhindered sliding of the hose into guide bed 2.

The housing 14 of the pump contains a cassette receptacle 13 designed as a recess in the housing (FIG. 2) for insertion of a replaceable cassette 15 (FIG. 1). A guide channel 15 b and a pump hose 16 connected to it, in which the fluid being conveyed is guided, are integrated in the cassette 15 depicted in FIG. 1. A loop- or arc-shaped section of the pump hose then protrudes from housing 15 a of the cassette. Several connection tubes 17 a, 17 b, 17 c are arranged on the top of the cassette 15, which can be connected to supply bottles for fluids being injected (for example, contrast agent). The connection tubes 17 a, 17 b, 17 c are connected to the pump hose 16 via the guide channel 15 b. A connector 16 a is arranged laterally on cassette 15, to which a patient tube can be connected in order to connect it to pump hose 16.

An unthreading device with a protrusion 8 protruding above the surface of carrier disk 1 is arranged on hose output 2 b, as is known from DE 10 2014 104 320 B3, to which reference is made here.

For operation of the hose pump, the section of the pump hose protruding from the cassette is introduced to the hose bed 2, the hose being guided by the guide rollers 5 and then running at limited distance and essentially parallel to the surface of the support disk 1 between the outer periphery of pinch rollers 3 and the counter bearing 4 as well as between the guide groove 11 of guide rollers 5 and counter bearing 4. The (radial) distance between the outer periphery of pinch rollers 3 is then chosen smaller than the diameter of the hose so that the hose is clamped between the outer periphery of pinch rollers 3 and counter bearing 4 with squeezing of the flexible hose.

During pump operation of the hose pump, the carrier disk 1 (and optionally the pinch rollers 3 and the guide rollers 5 arranged on it via a gear mechanism) is placed in rotation in conveying direction F by drive 7. In the embodiment example depicted in the figures, the carrier disk 1 is rotated clockwise during pump operation. The section of the hose lying in hose bed 2 is then pressed by the pinch rollers 3 against counter support 4 so that the hose is intermittently pinched and the fluid situated in the hose conveyed in the direction from hose input 2 a to hose output 2 b. The guide rollers 5 then ensure reliable and uniform positioning of a section of the hose in hose bed 2 by engaging the hose in guide groove 11 of guide rollers 5 and guiding it in so doing.

A threading device is expediently provided in the area of the hose input 2 a for threading of the section of the hose protruding from the cassette. This threading device can be formed by a motor-driven screw spindle, as is known from DE 10 2010 000 594 B4, to which reference is made here. A more cost-effective threading device that dispenses with the use of a motor-driven screw spindle is described in DE 10 2014 104320 A1, to which reference is made here.

During threading of the hose into the hose bed, the arrangement of pinch rollers 3 and guide rollers 5 on carrier disk 1 prevents the upstream section of the hose from slipping out of the guide groove 11 of the guide roller lying in the area of hose input 2 a during threading (this is guide roller 5 a in FIGS. 1 and 2). When the carrier disk is rotated, the pinch roller 3 a directly following this guide roller 5 a at the small angular distance 6, then presses the upstream section of the hose that has already been threaded by the leading guide roller 5 a against the counter support 4 and thereby fixes in hose bed 2 the position of the section of the hose already introduced into the hose bed. This prevents a somewhat too short hose from being strongly stretched during threading and from slipping out of the guide groove 11 of guide roller 5 a.

After threading of the section of the hose protruding from the cassette into the hose bed 2 in the manner described in DE 10 2014 104320 A1 (to which reference is made here), the pump can be operated to convey the fluid situated in the hose in its conveying direction F. For this purpose, the carrier disk 1 in the embodiment example illustrated here is rotated by drive 7 clockwise so that the pinch rollers 3 press the hose against the counter support 4 by pinching it and thereby transport the fluid situated in the hose in the conveying direction.

By guiding the hose in the hose pump according to the disclosure in the region of the hose output 2 b of the hose bed 2, it is ensured that the pinch roller passing by during pump operation (this is pinch roller 3 c in the drawings) only passes over the hose section inserted there when it is already completely unloaded because of the counter support 4 emerging there tangentially outward. The service life of the hose is thereby extended. In known hose pumps, there is the risk that a pinch roller will travel over the hose in the area of the hose output of the hose bed across the conveying direction F and still press it against counter support 4 so that increased flexing occurs and therefore increased mechanical loading of the hose material. Because of the higher mechanical loading, the hose more quickly loses its rigidity and must be replaced sooner since it can no longer withstand the pressure load.

The disclosure is not limited to the embodiment depicted in the drawing. For example, the number of pinch rollers 3 and guide rollers 5 can be chosen differently. However, it is expedient to provide equally many guide rollers and pinch rollers, for example, four pinch rollers 3 and four guide rollers 5, which are arranged in alternating sequence on the carrier disk 1 so that their axes lie on a circular path running concentrically around the axis of rotation A of carrier disk 1. The angular distances between the pinch rollers and between the guide rollers are then equidistant from each other. With four guide and pinch rollers, this angular distance between the guide and pinch rollers is 90°. 

What is claimed is:
 1. A hose pump to convey a fluid guided in a hose, the hose pump comprising a hose bed having a counter support, a carrier disk rotatable relative to counter support, a plurality of pinch rollers arranged equidistant from each other in a peripheral direction on the carrier disk and a plurality of guide rollers arranged equidistant from each other in the peripheral direction on carrier disk, wherein one of the plurality of guide rollers is arranged between two consecutive pinch rollers in the peripheral direction of the carrier disk and the pinch rollers press a hose inserted into the hose bed against the counter support, when the carrier disk is rotating in a conveying direction, while pinching the hose against the counter support to transport the fluid in the hose in the conveying direction, wherein an angular distance between a guide roller and a pinch roller preceding said guide roller in the conveying direction is greater than an angular distance between said guide roller and a pinch roller following said guide roller in the conveying direction.
 2. The hose pump according to claim 1, wherein the angular distance between a guide roller and a pinch roller following said guide roller in the conveying direction is less than 60° and especially no more than 45°.
 3. The hose pump according to claim 1, wherein the angular distance between the guide roller and the pinch roller preceding said guide roller in the conveying direction is greater than 60° and especially at least 75°.
 4. The hose pump according to claim 1, wherein at least three pinch rollers and at least three guide rollers are arranged on carrier disk.
 5. The hose pump according to claim 1, wherein a cylinder protruding above the surface of the carrier disk is arranged in the center of the carrier disk coaxial to the axis of rotation, the outside diameter of the cylinder reaching roughly the outer periphery of the pinch rollers and the guide rollers lying radially farther outward.
 6. The hose pump according to claim 5, wherein the radial distance between the outer surface of cylinder and the outer periphery of the pinch rollers and the guide rollers is smaller than the diameter of the hose inserted into the hose bed.
 7. The hose pump according to claim 1, wherein the pinch rollers are designed to be essentially cylindrical and to have a smooth outer surface, the outer periphery of the pinch rollers being formed by the smooth outer surface.
 8. The hose pump according to claim 1, wherein the guide rollers are essentially cylindrical and have a guide groove running in the peripheral direction on the outer periphery.
 9. The hose pump according to claim 8, wherein the guide groove of each guide roller has a semicircular cross section.
 10. The hose pump according to claim 1, wherein the pinch rollers and/or the guide rollers are mounted to rotate on the carrier disk.
 11. The hose pump according to claim 1, wherein a hose inserted into the hose bed lies on a guide surface formed by the surface of the carrier disk.
 12. The hose pump according to claim 1, wherein the axis of rotation of the carrier disk and the axes of the pinch rollers and the guide rollers are parallel to each other.
 13. The hose pump according to claim 1, wherein the carrier disk and/or the pinch rollers mounted to rotate on the carrier disk and/or the guide rollers mounted to rotate on the carrier disk are placed in rotation by a drive, when the hose pump is running.
 14. The hose pump according to claim 1, in which the magnitude of the relative angular difference between the angular distance between a guide roller and the pinch roller preceding said guide roller in the conveying direction and the angular distance between said guide roller and the pinch roller following said guide roller in the conveying direction lies in the range from 0.2 to 0.5.
 15. The hose pump according to claim 1, in which the magnitude of the relative angular difference between the angular distance between a guide roller and a pinch roller preceding said guide roller in the conveying direction and the angular distance between said guide roller and the pinch roller following said guide roller in the conveying direction lies at 0.25.
 16. The hose pump according to claim 1, in which the magnitude of the relative angular difference between the angular distance between the guide roller and the pinch roller preceding said guide roller in the conveying direction and the angular distance between said guide roller and the pinch roller following said guide roller in the conveying direction lies at 0.33.
 17. The hose pump according to claim 1, wherein the counter support with an essentially circular segment shape emerges tangentially outwards in the area of the hose output of hose bed.
 18. A hose pump to convey a fluid guided in a hose, the hose pump comprising a hose bed having a counter support, a carrier disk rotatable relative to counter support, a plurality of pinch rollers arranged equidistant from each other in a peripheral direction on the carrier disk and a plurality of guide rollers arranged equidistant from each other in the peripheral direction on carrier disk, wherein one of the plurality of guide rollers is arranged between two consecutive pinch rollers in the peripheral direction of the carrier disk and the pinch rollers press a hose inserted into the hose bed against the counter support, when the carrier disk is rotating in a conveying direction, while pinching the hose against the counter support to transport the fluid in the hose in the conveying direction, wherein a cylinder protruding above the surface of the carrier disk is arranged in the center of the carrier disk coaxial to the axis of rotation, the outside diameter of the cylinder reaching roughly the outer periphery of the pinch rollers and the guide rollers lying radially farther outward.
 19. The hose pump according to claim 18, wherein the radial distance between the outer surface of the cylinder and the outer periphery of the pinch rollers and the guide rollers is smaller than the diameter of the hose inserted into hose bed. 